Instrumentation.ts never executes on deployments

I have a Remix application deployed on Vercel.

I recently realized @sentry/remix wasn't fully instrumented on the Remix server. I added an instrumentation.ts file and started simply with some logging:

1import * as Sentry from '@sentry/remix';23console.log('VERCEL INSTRUMENTATION FILE');45export function register() {6  console.log('VERCEL INSTRUMENTATION FILE REGISTERED');78  Sentry.init({9    dsn: process.env.SENTRY_DSN,10    environment: process.env.NODE_ENV,11    tracesSampleRate: 1.012  });13}

However, I don't see these logs appear in the Vercel logs, and I do not see the instrumentation file in any of the build artifacts under Sources (in either Source or Output).

I'm using the @vercel/remix package and the remix vite vercel preset. Not sure what I need to do to ensure the instrumentation file is included in the build artifacts. Couldn't find any documentation for Other frameworks other than examples of the file structure.

Hi Atticus

instrumentation.ts is a Next.js feature

Sentry has docs here for how to instrument a Remix app. If you don't have entry.server.tsx in your codebase, you can run npx remix reveal to make it appear

https://docs.sentry.io/platforms/javascript/guides/remix/

Ah, I had noticed there were a few parts of the docs that mentioned "Other Frameworks", so I assumed it was vercel level.

Screenshot 2025-07-28 at 9.12.58 AM

The key detail Sentry calls out for its instrumentation is that it runs before the application runtime begins. The problem with adding it in entry.server.tsx is that the module has already been loaded by Vercel's server entrypoint, and instrumentation is applied too late.

I could solve this if i can get an instrumentation file to belong as part of the build output, and instruct vercel import it before the application module is loaded, but I'm not sure if this is possible

Screenshot 2025-07-28 at 9.15.30 AM

This GH discussion has a few mentions of the problem as well https://github.com/remix-run/remix/discussions/1522#discussioncomment-5982445

In particular, issue is that the instrumentation has to run before Vercel's server-index.mjs imports the remix build:

1import {2  createRequestHandler as createRemixRequestHandler,3  createReadableStreamFromReadable,4  writeReadableStreamToWritable,5  installGlobals,6} from '@remix-run/node';7import * as build from './index.js';89installGlobals({10  nativeFetch:11    (parseInt(process.versions.node, 10) >= 20 &&12      process.env.VERCEL_REMIX_NATIVE_FETCH === '1') ||13    build.future.unstable_singleFetch,14});1516const handleRequest = createRemixRequestHandler(17  build.default || build,18  process.env.NODE_ENV19);2021function toWebHeaders(nodeHeaders) {22  const headers = new Headers();2324  for (const key in nodeHeaders) {25    const header = nodeHeaders[key];26    // set-cookie is an array (maybe others)27    if (Array.isArray(header)) {28      for (const value of header) {29        headers.append(key, value);30      }31    } else {32      headers.append(key, header);33    }34  }3536  return headers;37}3839function toNodeHeaders(webHeaders) {40  return webHeaders.raw?.() || [...webHeaders].flat();41}4243function createRemixRequest(req, res) {44  const host = req.headers['x-forwarded-host'] || req.headers.host;45  const protocol = req.headers['x-forwarded-proto'] || 'https';46  const url = new URL(req.url, `${protocol}://${host}`);4748  // Abort action/loaders once we can no longer write a response49  const controller = new AbortController();50  res.on('close', () => controller.abort());5152  const init = {53    method: req.method,54    headers: toWebHeaders(req.headers),55    signal: controller.signal,56  };5758  if (req.method !== 'GET' && req.method !== 'HEAD') {59    init.body = createReadableStreamFromReadable(req);60    init.duplex = 'half';61  }6263  return new Request(url.href, init);64}6566async function sendRemixResponse(res, nodeResponse) {67  res.statusMessage = nodeResponse.statusText;68  res.writeHead(69    nodeResponse.status,70    nodeResponse.statusText,71    toNodeHeaders(nodeResponse.headers)72  );7374  if (nodeResponse.body) {75    await writeReadableStreamToWritable(nodeResponse.body, res);76  } else {77    res.end();78  }79}8081export default async (req, res) => {82  const request = createRemixRequest(req, res);83  const response = await handleRequest(request);84  await sendRemixResponse(res, response);85};